The invention relates to a two-chamber compressed-gas pack consisting essentially of a can body and of a concertina with a bottom and a collar reversing during movement in the can body, and to a process for producing it.
A two-chamber compressed-gas pack is a container for receiving and dispensing liquid and pasty products under pressure and consists of a rigid, usually metal outer container, namely the can body, in which a concertina with a rigid bottom and a reversible collar is fastened in such a way that two chambers are formed, one being filled with the extraction product and the other with a propellent gas under increased pressure or a pressure-generating fluid. The pressure of the propellent gas is relieved by means of a valve which is located on the product side and which allows the product to flow out of the pack when it is actuated.
The advantage of containers of this type in comparison with known spray cans is that the propellant expelling the product remains in the container and, furthermore, does not come in contact with the product. The lastmentioned fact is very important especially when the product is a foodstuff, cosmetic agent or medicine.
However, where the two-chamber compressed-gas pack is concerned, problems arise repeatedly in the region of the point of connection of the concertina to the outer container or during its handling. According to U.S. Pat. No. 3,415,425, the collar which reverses during movement in the can body is incorporated by means of its orifice edge in the bottom seam of the three-part outer container consisting of a bottom, a cylinder and a valve plate, in order to guarantee the necessary sealing between the product chamber and the propellant chamber. In a similar way, according to U.S. Pat. No. 3,620,420, the orifice region of the reversing collar is gripped in, among other things, the seam of the cover for fastening the valve plate or glued on in the upper part of the can body. In addition, the introduction of a tubular supporting ring in the region of the reversing collar is proposed, so that the latter is guided in a controlled manner and is not pressed radially inwards, which could have an influence on the discharge of the product and the sealing effect of the concertina.
The essential disadvantages of two-chamber compressed-gas packs according to the state of the art described are that multipart can bodies are absolutely unavoidable and/or that the inserted supporting ring builds up a very high frictional force which impedes the discharge of the product because of the lack of differential pressure between the chambers. Moreover, the outlay in terms of material for the concertina and possibly also the supporting ring is considerable.